Palaeontologia Electronica http://palaeo-electronica.org AGAMID LIZARDS FROM THE EARLY EOCENE OF WESTERN INDIA: OLDEST CENOZOIC LIZARDS FROM SOUTH ASIA G.V.R. Prasad and Sunil Bajpai G.V.R. Prasad. Department of Geology, University of Jammu, Jammu – 180 006, India. [email protected] Sunil Bajpai. Department of Earth Sciences, Indian Institute of Technology, Roorkee – 247 667, India. [email protected] ABSTRACT The discovery of agamid lizards from the Lower Eocene (ca. 53 Ma) deposits of Vastan Lignite Mine, western India, is reported, based on a number of dentaries and one maxilla. There are at least two distinct sets of dentary bones with varying morphol- ogies, indicating the presence of two different taxa, Vastanagama susani gen. et sp. nov. and Tinosaurus indicus sp. nov. The new finds represent the oldest known occur- rence of agamid lizards in the Cenozoic of South Asia. Though tricuspid, the teeth on the dentaries and maxilla of V. susani gen. et sp. nov. and T. indicus sp. nov. appear more closely related to Tikiguania estesi, a Late Triassic taxon from India, than to the various species of Tinosaurus known from the Paleogene of North America, Europe and Asia. Differences include the development of lateral cuspules on the posterior teeth and the presence of a broad, flat or convex platform-like subdental ridge on the dentaries of V. susani gen. et sp. nov. The significance of these fossils in the context of ‘Out-of-India’ and ‘In-to-India’ paleobiogeographic hypotheses is discussed. KEY WORDS: Agamid, lizard, Cambay shale, Early Eocene, new species, biogeography INTRODUCTION and references therein); from the early Middle Eocene Kuldana Formation of northern Pakistan In the Indian subcontinent, early Tertiary conti- (Thewissen et al. 2001), and from the Lower nental vertebrates have long been known from the Eocene coal-bearing Ghazij Formation of Bal- upper part of the Subathu Formation (early Middle uchistan, western Pakistan (Gingerich et al. 1997, Eocene, ca. 47 Ma) of the Kalakot area in the state 1998, 2001). More recently, continental vertebrate- of Jammu and Kashmir, and from its type section yielding horizons have been discovered in Lower near Subathu, Himachal Pradesh (Kumar 2000 Eocene deposits (Cambay Shale) in the lignite PE Article Number: 11.1.4A Copyright: Society of Vertebrate Paleontology March 2008 Submission: 10 July 2007. Acceptance: 29 January 2008. Prasad, Guntupalli V.R. and Bajpai, Sunil, 2008. Agamid Lizards from the Early Eocene of Western India: Oldest Cenozoic Lizards from South Asia. Palaeontologia Electronica Vol. 11, Issue 1; 4A:19p; http://palaeo-electronica.org/paleo/2008_1/134/index.html PRASAD & BAJPAI: EOCENE LIZARDS FROM INDIA Figure 1. Location map of the fossil-bearing Vastan Lignite Mine, Surat District, Gujarat. mines of District Surat, Gujarat state, western India onycteris?, Hassianycteris, Cambaya). Additional (Figure 1). Initially known from fish remains mammalian faunas, comprising hyaenodontids, (Samant and Bajpai 2001, Bajpai and Kapur 2004, tapiromorphs, primates, rodents, condylarths and Rana et al. 2004), the vertebrate fauna recovered insectivores, have been described by Kapur (2006) from these mines, particularly that from Vastan, is and Das (2007). diverse and now represented by amphibians, liz- The terrestrial vertebrate-bearing strata from ards, snakes, crocodiles, turtles, birds and mam- Vastan have been dated as Lower Eocene (Middle mals (Bajpai et al. 2005a, b, c, Rana et al. 2005, Ypresian, ca. 52 Ma), based on the presence of the Bajpai et al. 2006a, Kapur 2006, Rose et al. 2006, benthic foraminifer Nummulites burdigalensis (Baj- Das, 2007, Mayr et al. 2007, Smith et al. 2007, col- pai and Kapur 2004, Rana et al. 2005). N. burdiga- lections under study at IIT, Roorkee). Until now, lensis forms part of the Shallow Benthic Zone 10, only the mammalian fauna of the Vastan Lignite corresponding to the planktic foraminiferal zone P6 Mine has been described in detail (Bajpai et al. (in part) and P7 of Serra-Kiel et al. (1998). How- 2005a, b, c, Rana et al. 2005, Bajpai et al. 2006a, ever, recent work on Vastan foraminifers (Sara- Rose et al. 2006, Smith et al. 2007). The placental vanan 2007; see also Bajpai et al. 2007) suggests mammal fauna of this site includes cambaythere that the species previously identified as N. burdiga- perissodactyls (Cambaytherium bidens, C. lensis may actually pertain to N. globulus. More thewissi, C. minor, Cambaytherium sp. A, Kalithe- importantly, dinoflagellate cysts, though rare in the rium marinus), dichobunid artiodactyls (Gujaratia Vastan samples, include two temporally significant indica), palaeoryctids (Anthraryctes vastanensis), taxa: Muratodinium fimbriatum and Hystrichos- cimolestids (Suratalestes gingerichi), apatemyids phaeridium tubiferum (V. Prasad and R. Garg, per- (Frugivastodon cristatus), insectivores (Vastania sonal commun., Birbal Sahni Institute of sahnia), adapiform and omomyid primates (Marc- Palaeobotany, Lucknow, India; see Bajpai et al. godinotius indicus and Vastanomys gracilis) and 2006b). Considered together, the benthic foramini- chiropterans (Icaronycteris, Protonycteris, Archae- fer and dinoflagellate data suggest a somewhat 2 PALAEO-ELECTRONICA.ORG older age (Early Ypresian, ca. 53.5 Ma) for the Vas- Type Species. Vastanagama susani sp. nov. tan vertebrates, making it the oldest known conti- Holotype. IITR/ SB/ VLM 1050, left dentary. nental vertebrate fauna in the Cenozoic of Southern Asia (see Bajpai et al. 2007). This is the Referred Specimens. IITR/SB/VLM/793, left den- best age estimate possible at present, but confir- tary, IITR//SB/VLM/ 886 right dentary. mation is required from additional data. Horizon & Locality. Lower Eocene Cambay Shale Cenozoic squamates of South Asia are of Vastan Lignite Mine, District Surat, Gujarat state, extremely poorly known. Rage (1987) reported two India. fragmentary teeth of Middle Eocene agamid lizards from Pakistan. The presence of lizards in the Vas- Vastanagama susani sp. nov. tan fauna was recently mentioned (Bajpai et al. Specific Diagnosis. Same as for the genus. 2005b, Rose et al. 2006), but the material has not yet been described or illustrated. Here we describe Etymology. The species is named in honor of Dr. two new species of agamid lizards, one represent- Susan E. Evans. ing a new genus Vastanagama, and the second Description. IITR/SB/VLM/1050 (Figures 2.3-4, belonging to Tinosaurus. The identifications are Figures 3.1-4, Figures 4.1-4) is a reasonably well- based on a number of dentaries and a maxillary preserved left dentary representing the anterior fragment found in association with the mammal and middle regions. The ventral margin of the den- fauna. These fossils represent the oldest known tary is more or less straight. The alveolar margin lizards from the Cenozoic of South Asia. Older, rises regularly from anterior to posterior. The lateral pre-Cenozoic records from India include those face of the dentary is convex and bears two shal- from the Jurassic Kota Formation (Evans et al. low depressions possibly representing the nutrient 2002) and a recently described Late Triassic form foramina (Figure 2.4). The smaller of the two from the Tiki Formation (Datta and Ray 2006). depressions lies ventral to the first acrodont tooth, The material described in this paper is housed whereas the larger posterior depression is posi- in the Vertebrate Paleontology Laboratory, Depart- tioned ventral to the third pleuroacrodont tooth. In ment of Earth Sciences, Indian Institute of Technol- dorsal view, the anterior end of the dentary is ogy, Roorkee, under the acronym IITR/SB/VLM. slightly curved medially. In medial view, a broad and slightly convex to flat, platform-like sub-dental SYSTEMATIC PALEONTOLOGY ridge occurs between the alveolar margin and the Meckelian fossa (Figure 2.3). Anteromedially this Order SQUAMATA Oppel, 1811 ridge bears a vertically oriented and ventrally slop- Superfamily ACRODONTA Cope, 1864 ing, raised, subspherical symphyseal facet (Figure Family AGAMIDAE Gray, 1827 2.3, Figures 3.2-4). The Meckelian fossa is broad Genus VASTANAGAMA gen. nov. posteriorly and tapers anteriorly. The tip of the Meckelian fossa closes before terminating poste- Generic Diagnosis. Dentary small (preserved rior to the posteroventral border of the symphyseal length 9.20 – 9.60 mm); three pleurodont teeth, surface (Figure 2.3). The lower margin of the den- recurved third pleurodont tooth followed by tricus- tary bears a long, narrow facet for the angular. This pid, acrodont and pleuroacrodont teeth with incipi- facet extends anteriorly to the level of the second ent development of lateral cuspules that are pleuroacrodont tooth. No splenial bone is discern- smaller in size than the central cusp as compared ible. to those of Tinosaurus; relatively deep anterior part The tooth-bearing surface consists of three of the dentary; differs from all known taxa of aga- conical, pleurodont teeth anteriorly that increase in mid lizards in having a subspherical, vertically ori- size posteriorly. The tips of the first and second ented, ventrally sloping symphyseal facet covering pleurodont teeth are broken. The third pleurodont almost the entire anterolingual face of the dentary tooth is slightly recurved and possibly represents a bone; broad and slightly convex to flat, platform- caniniform tooth. The pleurodont teeth are immedi- like subdental ridge between the alveolar margin ately followed by three triangular, labiolingually and the dorsal margin of the Meckelian fossa; and compressed acrodont teeth and five pleuroacro- close spacing of teeth. dont teeth. A very short diastema is present Etymology. The genus is named after the Vastan between the pleurodont and acrodont teeth (Fig- Lignite Mine from where the specimens were ures 2.3-4). The bases of the acrodont teeth are in recovered. close contact with each other and their long axes 3 PRASAD & BAJPAI: EOCENE LIZARDS FROM INDIA Figure 2. Line drawings of Vastangama susani gen.et sp.nov. IITR/SB/VLM/793, left dentary, 1. medial view, 2. lateral view. IITR/SB/VLM/1050, left dentary, 3. medial view, 4. lateral view. Hatched area marks broken areas on the bone.